Re: [PATCH] virtio-spec: clarify ro/rw bits and updating rule of virtio-net status field

From: Rusty Russell
Date: Tue Mar 20 2012 - 19:42:07 EST


On Wed, 21 Mar 2012 00:48:05 +0200, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> On Tue, Mar 20, 2012 at 09:35:18PM +1030, Rusty Russell wrote:
> > On Tue, 20 Mar 2012 14:20:21 +0800, Jason Wang <jasowang@xxxxxxxxxx> wrote:
> > > This patch clarifies VIRTIO_NET_S_LINK_UP as a read-only bit and
> > > VIRTIO_NET_S_ANNOUNCE as a read-writable bit. Also introduce the write 1 to
> > > clear semantics for all read-writable bits of config status field. This could
> > > help to reduce the config status field updating race between host and guest and
> > > also simplify the implementation.
> > >
> > > Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> >
> > This approach assumes an active config field, which neither lguest nor
> > S/390 have.
> >
> > Thanks,
> > Rusty.
>
> What does 'active' mean in this context?

It means you are assuming that writes to the config field trap to the
host.

Rusty.
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